1. Field of the Invention
This invention relates to integrated circuit design, and particularly to circuit placements on an integrated circuit chip.
2. Background
The motivation for the development of an improved method stemmed from the real life case of a particular netlist containing over 800,000 nets. Using the existing approach, a path extraction report request was initiated for 20,000 nets, a small fraction of the design. After 96 hours, the requested report generation was terminated because it had not successfully run to completion. The improved method, which is described in detail below, was then implemented and performed against the same netlist as before. Using the same computing power, the required path information for the entire netlist was extracted in under 20 minutes. As described in detail below, a total of 5 timing reports are required in order to fully compute the netlist path characteristics. They are independent reports that can be generated in parallel to further reduce run time when compared to serial execution.
As today's chip designs continue to grow in size and complexity, so too do the netlists that represent them. As a result, comprehensive extraction of path related information within these netlists can be extremely time consuming. A method is required to enable extraction of key path characteristics from netlists in order to drive chip design methodologies like PISCES which is described in U.S. Ser. No. 10/890,463, now U.S. Pat . No. 7,120,888 filed Jul. 12, 2004, and entitled “Method, System and Storage Medium for Determining Circuit Placement”. It is to this need of PISCES that this application is directed.
The vast permutations required to collect such information makes extracting these path characteristics impractical when using traditional timing path trace algorithms. Depending on the topology of the combinational logic there could be a multitude of sub-paths between the launch and capture points. The number of sub-paths can grow exponentially in nature which makes extraction of the entire set of sub-paths time prohibitive. An improved method is required in order to be able to extract key path characteristics from the netlist in real time.